Coupled Scholte modes supported by soft elastic plates in water.

Localized acoustic surface waves supported by a "soft" elastic plate in water are explored. Unlike many materials, such as aluminum, for soft interfaces the Scholte wave, a localized interface wave, has a speed well below that of sound in water, and the energy of the Scholte wave is no longer mainly localized to the water. We note that the Scholte velocity is largely independent of Poisson's ratio in the solid, and rather than the bulk speeds of sound, the ratio between the Young's modulus and the density of the solid may better indicate whether an interface is soft. The behavior of the coupled Scholte modes along a thin plate with soft interfaces are investigated. It is demonstrated, and experimentally verified using acrylic plates underwater, that for soft interfaces, the symmetric coupled Scholte mode exhibits dispersive behavior, and deviates from the Scholte and the fluid velocities at low frequencies.

The destroyed elbow.

Surgeons need an advanced knowledge of upper extremity anatomy and function to care for the destroyed elbow. This paper describes strategies for evaluating and treating this severe injury. Outcomes can be optimized with contemporary techniques and technologies. Surgeons need to instill realistic expectations in patients with advanced compromise.

Atraumatic palmar midcarpal dislocation in a skeletally immature adolescent with hemiatrophy.

We report a late presentation of a palmar midcarpal dislocation in an adolescent female with open growth plates who had no history of antecedent wrist injury. Midcarpal arthrodesis improved function and eliminated progressive pain.

The distal radioulnar joint capsule: clinical anatomy and role in posttraumatic limitation of forearm rotation.

Posttraumatic limitation of forearm rotation can be the result of pathology at any location along the forearm axis. Scar contracture of the distal radioulnar joint (DRUJ) capsule, independent of the triangular fibrocartilage complex (TFCC), is one of the sources that may influence the pronosupination arc. We dissected the wrists of 8 fresh-frozen cadaver specimens to characterize the precise anatomy, relationships, and dynamic characteristics of the entire DRUJ capsule. Additionally, we performed surgical DRUJ capsulectomy in 9 patients with recalcitrant limited forearm pronosupination that was unattributable to dysfunction at any other anatomic forearm location. We conclude that (1) the DRUJ capsule is a defined entity, separate from the triangular fibrocartilage, that is highly specialized to accommodate the distal ulna in forearm rotation; (2) in patients who have restored osseous anatomy after trauma, but have failed to regain pronosupination after maximal rehabilitation, the DRUJ capsule can be identified as the source of the limitation; and (3) DRUJ capsulectomy can markedly improve the arc of forearm rotation in carefully selected patients.

A systematic approach to handling the distal radio-ulnar joint in cases of malunited distal radius fractures.

The distal radio-ulnar joint (DRUJ) is often the site of persistent symptoms after malunion of distal radius fractures. These malunions alter load transfer across the ulnocarpal joint, disturb DRUJ kinematics, and result in joint incongruity at the sigmoid notch. Treatment of distal radius malunions must not only correct position of the radial platform and joint incongruity but also restore anatomic relationship at the DRUJ. A systematic approach to the surgical reconstruction of these multiplanar deformities using clinical and radiographic parameters is outlined.

Disorders of the forearm axis.

Forearm pronosupination is a complex, integrated activity that demands specialized function of all structures between the elbow and wrist. This article describes the forearm axis as a comprehensive concept to unify these relationships. The anatomy and biomechanics of the forearm axis are reviewed. Pathologies that affect the entire axis are summarized.

A comprehensive approach to surgical management of the type IIIA hypoplastic thumb.

In order to adequately identify pathologic anatomy and effectively reconstruct 14 type IIIA hypoplastic thumbs, a comprehensive clinical evaluation and surgical approach was employed. Eleven patients had congenital differences in the forearm, while all patients had anomalies in the wrist, hand, and digits. In addition to well-described interconnections between the flexor pollicis longus and the extensor pollicis longus, and thenar muscle hypoplasia, the authors observed duplication of musculotendinous units, anomalous muscles between the thumb and index rays, and abnormal insertions or dense adhesions along tendons as proximal as the forearm level. Successful reconstruction required an extended approach from the digit to the forearm, through which division of abnormal connections, reorientation of tendons, and lysis of adhesions was performed. Opposition transfer was needed in only 8 of the patients after the other pathologies were treated. Web-space deepening and ulnar collateral ligament reconstruction was performed when indicated. Improvement in function and appearance was achieved.

Finger polydactyly.

Polydactyly is one of the most common congenital differences. Duplications of the index finger, central rays, and small digit each have unique characteristics and associations. Complex anomalies such as the mirror hand and pentadactyly represent specialized forms of polydactyly. The goal of reconstructing a functional hand is met by appreciating the anatomic variations and systemic implications, then employing the challenging technical and intellectual concepts described.

Atypical hand infections.

The diagnosis and treatment of an atypical hand infection present a distinctive challenge for the hand surgeon. Infections caused by these uncommon organisms occur more often in immunocompromised patients. This article emphasizes the salient features of mycobacterial, nocardial, and fungal infections of the hand. With an accurate and timely diagnosis, appropriate surgical and pharmacologic treatment may eradicate these unusual infections.

The classification and treatment of heterotopic ossification about the elbow and forearm.

Successful treatment of HO about the forearm and elbow relies on a working understanding of the risk factors, the pathophysiology and pathoanatomy, and the potential role for reconstructive procedures. These elements must be combined with a certain degree of flexibility in the approach to patients with a wide range of individual needs. Class I HO should be managed primarily with close observation, serial radiographs, and appropriate physical therapy regimens. The temporal relationship between the insult and the appearance of HO may modify the approach. When HO is noted within the first 6 weeks, use of anti-inflammatory agents is recommended; if the patient has developed limiting ectopic bone in the past, consideration should be given to a single dose of radiotherapy. In the 6-week to 3-month period, therapy is conducted to maintain full motion and an anti-inflammatory agent continued or started. We have not observed initial HO appearance after the third month. Class IIA HO can involve the anterior or posterior aspects of the elbow joint, or both. These groups are further divided into those limited by soft tissue (muscle and capsular contracture) and those blocked by bone (coronoid extension, humeroradial, humeroulnar, blocked olecranon fossa). The anterior group limited by soft tissue is addressed by capsulotomy, releases, and lengthenings. This group requires careful neurolysis and protection of vascular structures. For anterior bony bridges, resection is combined with capsulotomy. The location of the forearm "insertion" site of the new bone dictates alternative procedures such as interposition or radial head resection. The condition of the joint is usually preserved in these cases, but arthroplasty must always be considered when injury has led to joint derangement. Posteriorly, limitations in motion are caused by a contracted scarred triceps, capsular contracture, or bony impingement and synostosis. Treatment requires posterior capsular release and triceps tenolysis. Bridging bone is excised, the olecranon partially excised, and the olecranon fossa reestablished. Attempts should be made to preserve the fat pad of the olecranon fossa, which can act as an effective interposition material. Although characterized by limited pronosupination, class IIB HO can be located in any of the six distinct anatomic sites previously outlined. Simple resection, with or without interposition, is useful for a majority of the HO that is coincident with the interosseous membrane, but the areas at the proximal and distal extent of the forearm may demand special procedures to restore motion.(ABSTRACT TRUNCATED AT 400 WORDS)

Phosphorus nuclear magnetic resonance: a non-invasive technique for the study of muscle bioenergetics during exercise.

Phosphorus nuclear magnetic resonance (31P NMR) spectroscopy is a non-destructive analytical laboratory technique that, due to recent technical advances, has become applicable to the study of high-energy phosphate metabolism in both animal and human extremity muscles (in vivo). 31P NMR can assay cellular phosphocreatine, ATP, inorganic phosphate, the phosphorylated glycolytic intermediates, and intra-cellular pH in either resting or exercising muscle, in a non-invasive manner. NMR uses non-perturbing levels of radio-frequency energy as its biophysical probe and can therefore safely study intact muscle in a repeated fashion while exerting no artifactual influence on ongoing metabolic processes. Compared with standard tissue biopsy and biochemical assay techniques, NMR possesses the advantages of being non-invasive, allowing serial in situ studies of the same tissue sample, and providing measurements of only active (unbound) metabolites. NMR studies of exercising muscle have yielded information regarding fatigue mechanisms at the cellular level and are helping resolve long-standing questions regarding the metabolic control of glycolysis, oxidative phosphorylation, and post-exercise phosphocreatine re-synthesis. NMR is also being utilized to measure enzymatic reaction rates in vivo. In the near future, other forms of NMR spectroscopy may also permit the non-invasive measurement of tissue glycogen and lactate content.

Classification and treatment of postburn metacarpophalangeal joint extension contractures in children.

Two hundred and seventy-eight surgically treated postburn metacarpophalangeal joint extension contractures in children were reviewed. A classification system based on the limitation of passive metacarpophalangeal flexion was devised to direct surgical intervention and assess postoperative results. Type I (47%) digits demonstrated greater than 30 degrees of metacarpophalangeal flexion with the wrist fully extended, and scarring was generally limited to the dorsal skin. Type II (34%) digits demonstrated less than 30 degrees of metacarpophalangeal flexion with the wrist maximally extended, and scarring typically involved skin, dorsal apparatus, and metacarpophalangeal capsule. Type III (19%) digits were fixed in greater than 30 degrees of metacarpophalangeal hyperextension and often demonstrated incongruity or dorsal subluxation of the metacarpophalangeal joint. Improvement after reconstruction was seen in 95% of type I digits, 73% of type II digits, and 47% of type III digits. Failure to improve usually resulted from inadequate scar release/excision or from failure to release deep soft tissues (dorsal apparatus or metacarpophalangeal capsule). Thirty secondary procedures were done to improve an unsatisfactory result after the initial reconstruction. These included deep releases, metacarpophalangeal joint arthrodeses, and amputations. The ring and small fingers accounted for 65% of the digits in this study, 68% of the failures, and all seven amputations.

The bioenergetics of preservation of limbs before replantation. The rationale for intermediate hypothermia.

Of all tissues of the extremities, muscle is the least tolerant of ischemia. Hypothermia of tissue is considered beneficial for the maintenance of viability of muscle in amputated limbs before surgical replantation, but it has never been established that conventional cooling in an ice bath or its equivalent (temperature of tissue, approximately 1 degree Celsius) is the optimum level of hypothermia for minimizing metabolic derangement in ischemic muscle. In this study, we first defined the time course and level of metabolic derangement of muscle in twenty-eight ischemic hind limbs in cats at 22, 15, 10, 5, and 1 degree Celsius. The levels of adenosine triphosphate and phosphocreatine and the mean intracellular pH of the muscles in the lateral aspect of the thigh in each limb were monitored with phosphorus nuclear magnetic-resonance spectroscopy over time. The excised muscles from six freshly amputated legs of live humans were then similarly studied to determine whether muscles from cats and from humans exhibit comparable bioenergetic responses to hypothermic ischemia. A final series of ten ischemic hind limbs from cats was studied by nuclear magnetic resonance and muscle biopsy for direct biochemical assay of tissue energy metabolites to compare the metabolic benefits of two different methods of preserving limbs: continuous cooling in an ice bath, and a newly devised protocol for the rapid induction and maintenance of so-called intermediate (10 +/- 5 degrees Celsius) hypothermia of tissue. Ischemic skeletal muscle in cats exhibited a paradoxical metabolic response to extreme cold (1 degree Celsius). The rate of metabolic deterioration progressively declined with decreasing temperature of tissue to 10 degrees Celsius. However, at 5 degrees Celsius, no additional benefit was detected, and at 1 degree Celsius, there was a significant acceleration in the rates of degradation of adenosine triphosphate and phosphocreatine and in the production of lactate. The rate of degradation of adenosine triphosphate in human ischemic muscle was also faster at 1 degree Celsius than at 10 degrees Celsius. This paradoxical response is apparently due to a severe inhibition of the calcium pump of the sarcoplasmic reticulum of the muscle cell at temperatures of less than 5 degrees Celsius. The inhibition permits an efflux of calcium to the myofibrils, which stimulates both glycolysis and the degradation of adenosine triphosphate by myofibrillar adenosine triphosphatase.

Phosphorus nuclear magnetic resonance: a non-invasive technique for the study of muscle bioenergetics during exercise.

Phosphorus nuclear magnetic resonance (31P NMR) spectroscopy is a non-destructive analytical laboratory technique that, due to recent technical advances, has become applicable to the study of high-energy phosphate metabolism in both animal and human extremity muscles (in vivo). 31P NMR can assay cellular phosphocreatine, ATP, inorganic phosphate, the phosphorylated glycolytic intermediates, and intra-cellular pH in either resting or exercising muscle, in a non-invasive manner. NMR uses non-perturbing levels of radio-frequency energy as its biophysical probe and can therefore safely study intact muscle in a repeated fashion while exerting no artifactual influence on ongoing metabolic processes. Compared with standard tissue biopsy and biochemical assay techniques, NMR possesses the advantages of being non-invasive, allowing serial in situ studies of the same tissue sample, and providing measurements of only active (unbound) metabolites. NMR studies of exercising muscle have yielded information regarding fatigue mechanisms at the cellular level and are helping resolve long-standing questions regarding the metabolic control of glycolysis, oxidative phosphorylation, and post-exercise phosphocreatine re-synthesis. NMR is also being utilized to measure enzymatic reaction rates in vivo. In the near future, other forms of NMR spectroscopy may also permit the non-invasive measurement of tissue glycogen and lactate content.

Classification and treatment of postburn proximal interphalangeal joint flexion contractures in children.

Two hundred and sixty-four surgically treated proximal interphalangeal joint flexion contractures in children were reviewed. A classification system on the basis of contracture severity was devised to assess the efficacy of treatment. Contracture severity was determined from preoperative radiographs and physical examination. Eighty-eight percent of the digits were successfully treated (postoperative contracture less than 20 degrees). Unsatisfactory results (12% of digits) were directly proportional to the severity of the contracture and tended to occur in older children with large total body surface burns. The time interval between burn and contracture release did not correlate with contracture severity or therapeutic failure. The most common cause of an unsatisfactory result was failure to fully release the contracture.

Inhibition of testosterone production by rat Leydig cells with ethanol and acetaldehyde: prevention of ethanol toxicity with 4-methylpyrazole.

The toxic effects of ethanol and acetaldehyde on testosterone biosynthesis were examined in vitro using isolated Leydig cells prepared from adult rat testes. The ability of 4-methylpyrazole, an inhibitor of alcohol dehydrogenase, to prevent the toxic effects of ethanol on testosterone production was investigated. Ethanol was found to inhibit gonadotropin-stimulated testosterone production in a dose dependent fashion. Concentrations of ethanol (25 mg/100 reduce testosterone levels by 44% as compared to the controls. Acetaldehyde at micromolar concentrations also inhibited testosterone biosynthesis. The addition of 4-methylpyrazole to the culture medium prevented the toxic effects of ethanol as determined by testosterone production. These studies suggest that ethanol per se may not directly inhibit testosterone biosynthesis. Rather, it would appear that acetaldehyde, the first product of ethanol metabolism, may be responsible for the toxic effects of ethanol upon Leydig cells at least in vitro.